Electron discharge device



011-22, 1946. v A. H. LAIDIG f 2,409,694

Y Y ELEcTRoN DISCHARGE DEVICE l Filed June` 2G, 1942 s sheets-sheet l1 A ATTORNEY l El e1 a INVENTOR SM- lIl Oct. 22, 1946. A, H, LAIDlG 2,409,694

ELECTRON DISCHARGE DEVICE` Filed June v26', 1942 3 Sheets-Sheet 2 'ATTORNEY BY' A..

Oct. 22, 1946. A, H, LAlDlG 2,409,694

' ELECTRQN DISCHARGE DEVICE Filed Jima 26, 1942 3 Sheets-Sheet 5 61 z J9! "58 l l l A l 1 l l I 25. 5 i5 i I au' l j "a BY ALUM/YW ATTORNEY Patented Oct. 22, 1946 UNITED STATES PATENT OFFICE ELECTRON DISCHARGE DEVICE Alfred H. Laidig, Bloomfield, N. J., assgnor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 26, 1942, Serial No. 448,555

novel high frequency radio apparatus including hollow-body resonators.

The type of electron discharge device with which the present invention may be classified, consists essentially of two hollow conducting circuit members or resonators within which fields, comprising standing electromagnetic waves, are adapted to be set up by the passage of a stream of electrons through a restricted part thereof. The said members are so constructed that they have or may be adjusted to have the same resonant frequency. They are also so Aconstructed that electrons pass completely through the field of said restricted part of each member preferably within the period of a minute portion of a half-cycle of the operating resonant frequency ofthe cavity members. VWith the electric vector of the'electromagnetic field of each member acting along the line of travel of the electrons and upon the latter for a time preferably equal to a minute portionof one-half cycle, successive electrons of the stream will emerge from the restrict-` ed part of the initial hollow resonant member, referred to as the buncher, with minute variable velocities and will move through the eld-'free space separating the restricted parts of thetwo members, whereby a concentration o f electrons will form around electrons of normal velocity, that are preceded by slightly slower electrons and followed by slightly faster electrons. Likewise, diminished numbers of electrons will obtain b etween bunches consisting of electrons of nor mal velocity that are preceded by fast electrons and followed by slow electrons. Thus, the electrons of the stream pass a given point in waves of increasing and decreasing density, which waves are caused to. pass through the restricted part of the second hollow resonant member, referred to as the catcher, by virtue of the phase relationship between the buncher and the catcher grid voltages which in conjunction with equality, though not necessarily/,of the resonant frequency of the two members, electromagnetic waves are excited in the second or catcher member that are stronger at the expense of the direct current energy than those existing in the initial or buncher member. With proper coupling of the electromagnetic waves in thecatcher member with those of the buncher member, sustained electromagnetic oscillations will result, such coupling obtaining when proper electric and mag- 2 netic inter-connection is provided between resonators with proper phase relations between their respective fields, that is, when the electron groups pass the mid-point between the restricted portions or poles of the catcher of energy abstracting resonant member when the iield in that member is most strongly opposing the proper motions of the electrons therethrough. The majority of the modulated electrons, likewise, pass completely through the restricted portion of theA secondor catcher resonator, and enter a collector. Since the electron group gathers around the electrons of normal velocity which are preceded by slow electrons and followed by fast electrons, this group of normal velocity electrons should pass the mid-point in the field of the restricted portion of the buncher resonator when that field is changing from zero so that the following electrons will be assisted thereby.

Electron streams, in velocity modulated tubes, are of relatively high impedancev and match readily the resonators through which they pass. The high electron stream impedance is obtained by means of a high potential, but low stream current. This procedure in the microwave region of a few centimeters wavelength encounters difficulties by seriously limiting the output of the oscillators, etc. to i almost useless levels. Since practically there is a denite limit to the stream electron density the only other factor in increasing current is to increase the cross section area of thestream. However, in the prior art, as related to the short microwave region, the resonators are scaled down to such an extent that the oriiice area through which the stream passes is much restricted. This reduces the stream current.

The proportional magnitudes of theresonators and streams is at once evident if one considers, in the simplest case, an Eno mode in a cubical resonator, This designation refers to an electric vector parallel to the axis (having 11:0) the frequency of which is independent of the dimensions along this aXis (Z) and having only one mode of oscillation 4,with the longest possible wavelength, l, given by 2\/2a, wherein A designates wavelengths and adesignates the dimension from the center normal to a side of the cube. From this simple relation, we immediately see that, in the microwave region of present concern, the largest resonator dimension is of the order of a fraction of an inch at a few centimeters wave length.

rI'he effective Q of such a small resonator is appreciably nuenced by the extent of the orifice and this in fact varies approximately as t6/b3 (assuming plane waves which, of course, are not strictly existant in hollow resonators in general), where b is the area of all the orifices involved. Hence, the ratio of orifice to resonator surface must be kept as small as possible (even though there are modes of oscillation whose fields more or less avoid ,the orice) and this is not `possible rwith conventional methods of enveloping the resonators around electron streams, without serious loss in electron stream current and hence output.

An object of the present invention is accordingly to improve upon prior art structures to overcome effectively the deficiencies therein and particularly to increase power output in the microwave range with an increase rather than decrease in the size of mechanism employed.

A further object of the invention is to provide for a central collector toward which electrons converge from a ring-like cathode.

Another object of the invention is to enable the collector to be adequately cooled notwithstanding its central position.

A still further object of the invention is to provide a heater for the cathode adequately supported to have a circumferential position around the cathode and retained from physical contact with the cathode.

Still further objects will appear as the description proceeds both by direct recitation thereof and by implication from the Context.

In the accompanying drawings, wherein like numerals of reference indicate similar parts throughout the several views, and wherein preferred physical embodiments of the invention are disclosed by way of example;

Figure i is a perspective view of an electron discharge device embodying my invention;

Figure 2 is a vertical section on an axial plane as on line II-II of Figure 3;

Figure 3 is a sectional view on a plane perpendicular to the axis and taken midway of the length of the device, that is to say on a vertical line through the middle of Figure 2;

Figure 4 is a perspective View of o-ne of the grid cages;

Figure 5 is a longitudinal sectional view similar to Figure 2 showing a modification;

Figure 6 is a fragmentary sectional view on line VI-VI of Figure 5; and

Figure 7 is a fragmentary sectional view on line VII-VII of Figure 5.

In the specific embodiment of the invention illustrated in said drawings, the structure provides a generally cylindrical housing I0 the outward assembled form of which presents an outer cylinder I I of short length with a somewhat smaller cylinder I2 projecting axially therefrom at both ends and yet smaller cylinders I3 projecting from both ends of cylinder I2. The outer cylinder II constitutes the cathode and cathodeheater region, the next smaller or intermediate cylinder I2 provides the resonator and field-free area, whereas the small cylinders I3 afford a region for collection of the electrons. These several cylindrical portions of the housing as a group are vacuum sealed so that the entire interior may be an evacuated region with the housing constituting the envelope maintaining the vacuum.

The invention will first be described in a simple form, illustrated in Figures 1 and 2, to acquaint the reader with the subject matter generally, and then added detail will be discussed with reference to the remaining figures of the drawings.

As here shown, the inner cylinder I3 projects axially through the next larger or resonator cylinder I2 which in turn projects axially through the next larger or outer cylinder II. The construction is such that the outer cylindrical wall I4 of the resonator cylinder in Dart is the inner cylindrical wall for the annular outer cylinder. Similarly the outer cylindrical wall I5 of the inner cylinder I3 in part is the inner cylindrical wall for the annular resonator cylinder, Within outer cylinder II, and in the area around the common `portieri of cylindrical wall I4 is an annular ring of insulation I6, outwardlj7 flanged for supporting purposes and to provide an outer region fora vpair -of bus-bars Il engirdling the ring of insulation and held thereby from contact with each other or with the cylinder walls. Sealed input connections I8 are provided for said bus bars from the exterior of said outer cylinder. The circumferentially inner face of the insulation ring IS is preferably concave and provides adequate depth for reception of heater filament segments =I il shown as short coils of appropriate wire the ends of which project radially through the insulation ring and connect with the two bus-bars I'I. The several segments I9 are arranged, with proper insulative spacing, end to end, and accordingly compose a coiled heater making a full convolution, with each segment in electrical parallel to the others. Burning out of one filament segment accordingly does notl stop operation of the device .as a whole.

A ring-like cathode 26, having side flanges, is carried by said flanges upon said ring of insulation, the emitting portion of the cathode being radially inward from the heater and overlying both the heater and the concave face of the ring of insulation. The diameter of the inner circumference of the cathode is only slightly greater than the outside diameter of the next adjacent outer curved wall I4 of cylinder I2 which is provided with a circumferential opening 2I directly in front of the cathode. Electron emission from the cathode accordingly enters radially through said opening 2I in the common part of wall I4 bgtween outer cylinder II and resonator cylinder I Inwardly of the said circular or circumferential opening in said cylindrical wall I4 is an annular field-free space 22 defined by a pair of washer-like plates 23, spaced apart substantially the width of said opening. Said field-free space ris annular and extends in a radial direction from proximity of and between the cylindrical walls I4 and I5 of the resonator cylinder. The field-free space v22 is entirely within the confines of the resonator cylinder and the plates 23, accordingly divide the end portions of the cylinder from the middle portion forming the field-free space except for small circular gaps 24, 25 between the peripheries of the plates and cylindrical walls I4 and I5 respectively.

Resonator cylinder I2 has a washer-like or annular end wall 26 at each end thereof hermetically sealed with respect to cylindrical walls I4, I5 and parallel to each other and to the plates 23, within that cylinder. Between each said end wall and plate 23 nearest thereto, perpendicular to both is an intermediate wall 21 which is cylindrical and situated such that the volume of the resonator cylinder, exclusive of the area occupied by the field-free space, is substantially divided in half. Thus are provided two resonator chambers 28, 29 of which one, as 29, is radially within the other, each chamber being annular and the full length of cylinder I2 with a restricted central portion at gaps 24 and 25 respectively. Intermediate wall 21 is common to both of these resonator chambers and has an` aperture 30 through which extends a coupling loo'p 3l for maintaining resonance in the outer chamber from resonance of the inner one.

Cylindrical wall I5 .between resonator cylinder I2 and smaller cylinder I3 is peripherally slotted providing an opening 32 therethrough in close proximity to the space included between fieldfree space conning plates 23 so that electrons emitted from cathode 20 after passing through field-free space 22 continue into the smaller cylinder I3 through said opening 32. The openings 2| and 32 in the outer and inner cylindrical walls I4 and I5 of the resonator cylinder, as well as the openings to and from the eld-free space at the outer and inner peripheries of the aforementioned washer-like plates 23 have appropriate grids 33 thereacross. These grids may eachbe fabricated as a unit, appearing as a cage shown in detail perspective, view by Figure 4. The grids are of generally cylindrical construction, having end hoops 34 `and transverse stays 35 edgewise to the electron flow with desired interpositioning of grid wires 36 parallel to the stays to give appropriate grid area by wires and stays.

Within the small cylinder I3 is a generally cylindrical collector electrode 31 the structure of which is the same in all figures of the drawings. It is provided with a plurality of pyramidal cavi- ,ties 38 the bases of which open outwardly in proximity to the electron-passing opening 32 of the surrounding cylindrical wall I5 of said cylin- I der I 3. Projecting coaxially from opposite ends of this collector are pipes 39 having other pipes 40 within the same so that a cooling medium may be introduced, as through inner pipes 4I) to a cooling chamber 4I of the collector and returned outward for discharge by outer pipes 39. Said outer pipes 39 are sealed with respect to the collector and to metal caps 42 at outer parts of the pipes, these caps in turn having glassed seals 43 with the inner cylinder I3. This structure likewise constitutes an appropriate support for the collector.

In operation it will be understood that electrons emitted from the cathode travel in a direction radially inward of thev device and DaSS "5() through the first two grids33 which are separated by gap 24, and then into the field-free space. The resonance of chamber 28 affects the electrons in their said passage between the grids,

"modifying the electron stream such that some electrons pass through unaiected as to velocity, other electrons are minutely slowed down, and yet other electrons are minutely speeded up. The magnitude oi the modulation is partially dependent upon the eld strength-between the said grids. The electrons. modified as to velocity, continue their travel through the eld-free space 22 with the electrons having normal or unaiected speed overtaking previously dispatched somewhat slower electrons and in turn being overtaken by somewhat speeded-up electrons started at a later moment The proportional length, or radius, in direction of flow of the electrons, of the field-free vspace is such that the proper concentration or bunching of electrons takes place between the smaller. pair of grids 33 in the gap area 25. The electrons accordingly representl a concentration of energy in the said gap area 25 and are capable .of giving up energy to the second resonator chamber 29 when acted on byoscillating electric fields between the grids in the proper phase in accordance with classical theory. A small amount of this energy is utilized, as indicated above, as feed back through loop 3| to the lirst resonator chamber 28 in order to modify the flow of other electrons in the gap 24 between the larger rst pairof grids 33, so that the cycle of operations above explained may continue. Utilization of energy thus built up in inner or smaller diameter resonator chamber 29 is obtained by meansY of a suitable output connection such as the coaxial line coupling 44. .This coupling is preferably constructed as a copper tube 45 within a sleeve 4E. soldered or otherwise vacuum sealed through the resonator wall. The outer end of this sleeve is vacuum sealed to a sleeve 41 which virtually constitutes a continuation of the first sleeve 416 but of a material such as that sold under the trade name of Kovar which has a coeliicient of expansion substantially equivalent to that of borosilicate glass. A glass cap 48 is sealed to the outer end of this Kovar sleeve and completes the vacuum-tight enclosure. Copper tube 45 preferably extends from the resonator wall to the outer end of the Kovar sleeve and constitutes a good electrical conductor. A coaxial wire 49 extends through the tube, projecting at opposite ends thereof and providing a loop 5|) within the resonator and a loop 5I within the glass cap 48, the ends of the wire in each instance being secured to the next adjacent end of the copper tube. Other output connection, however, may be employed, as found desirable or expedient. It will be seen now that the present structure of the disclosed ultra high frequency device is very simple, due in large part to the compact cylindrical shape, that it `can be very accurately built, and when assembled is very rigid. These advantages are important to achieve a resonator structure pretuned in manufacture and without means for tuning in use.

In order that the device may be illustrated as capable of being tuned, I have shown an elaboration of the structure above described, by the illustration of Figures 5 to 7. Equivalent parts in this illustration have been identied by numerals heretofore used but with the addition of a prime mark on the numeral. While some of the parts illustrated in this elaboration are identical with parts shown and described in the more simple disclosure of Figures 1 to 4, and some parts are similar or equivalent thereto, it is believed that repetition of the above description will be found unnecessary. Suffice it to say that asbefore, a cylindrical cathode 2B is provided (shown in thisinstance as concave for focussing purposes), the cathode directing electrons through a rst pair of grids 33', a eld-free space 22', a second pair of grids 33' and thence to the co1- lector 31. Gaps 24' and 25' exist between the grids, and for tuning purposes it is desired to be .able to change the gap distance or spacing of the grids of each pair.

As a means `for accomplishing the tuning by change of grid relationship, I have shown both cylindrical walls I4 and I5' flexible and resilient, this being accomplished by corrugating those walls in a direction parallel to the cylinder axis. I likewise prefer to taper these cylindrical walls, that tapering being exaggerated in the drawings in order to emphasize its presence. The outer edges of these cylindrical walls are vacuum sealed, as before, to the end wall of the resonator cylinder I2.V Tuning is obtained by compressing the flexible walls in a direction toward the dening 7 plates 23 of the held-free space 22' or by permitting the flexible walls to move away from those plates by virtue of the resiliency of the said cylindrical walls.

Appropriate means for compressing or releasing the ,flexible walls is provided, and for fobtaining delicacy of tuning, the means vhere illustrated enables each ilexible wall to be exed irrespective `of flexing of any other cylindrical wall portion. As shown, a protruding cylindrical neck 53, externally threaded as at 52, is provided xed with respect to the end wall of the resonator cylinder and forming substantially a .continuation of cylindrical wall I4. A smaller collar 54 of similar nature but internally threaded at 55 is l;

provided xed to the end wall of the resonator cylinder and protruding vtherefrom substantially as a continuation of cylindrical wall I5. collars, as well as associated parts about to be described, appear at both ends of the device, but for simplicity of description the construction at one end only will be given in detail. An adjusting knob `56 internally threaded at 51 to .mesh with threads 52 of the collar 53 is provided in the form of a ring concentric with the axis of the device. Similarly, adjusting knob 58 of smaller diameter and having external threads v59 to mesh with threads 55 of collar 54 is also provided concentric with the axis of the device.

A flat ring 6B is carried at its inner periphery in an appropriate peripheral groove in knob 5B, said knob being shown as of split nature for enabling the ring 60 to be inserted and retained within the groove. The knob may be rotated with respect to the ring, but since rotation of the knob moves the knob axially by virtue of the threaded mounting thereof, rotation of said knob will accordingly move the ring laterally without necessitating rotation of said ring. Similar to the provision of outer ring 60, an inner `ring 6| is provided in conjunction with smaller knob 58. Around the .outer cylindrical wall M' of the resonator in engagement with the peaks of the corrugations thereof is a band 62 vparallel to and of substantially the same diameter as the aforementioned adjusting ring 60. At suitable intervals are provided slidable posts 63 perpendicular to and interconnecting said yband and ring. Consequently movement of the ring in a direction longitudinally of its axis also moves the band and since the band engages the sloping surface of the resonator cylindrical wall, such movement in an inward direction willcompress that Wall and move its grid inwardly, whereas movement of the band axially outward Will enable ,the resonator wall to resiliently expand radially and thus adjust the grid to a new position. It is to be understood that the grid in this instance is composed of transverse stays and wires secured directly to the resonator wall so that the expansion and contraction above mentioned may take place. Sim- These ilarlyy the inner resonator wall I5' has a band f 64 in engagement therewith, said .band being parallel to and of substantially the same diameter as inner adjusting .ring 6|. This band and ring are connected at intervals by posts 65 thus enabling the inner resilient wall I5 of the resonator to be adjusted and to obtain adjustment of its grid 33'.

All of said posts 53 and 65 are slidably mounted in rigid bearings 66 and are rendered vacuum tight and yet movable by virtue of appropriate flexible diaphragms 61. It is intended that each revolution of the respective knob shall transmit very slight movement to the end of the grid associated with the ,particular knob. As a result, very'ne tuning .may -be obtained and maintained. Equal manipulation `of corresponding knobs at opposite ends .of the device keeps the grids yparallel, butit will vbe found that fractional tuning can lbe obtained by turning only-one knob a short ways and thus have .the grid very slightly out of parallel with its companion grid. Theknobs .are preferably suitably marked, as `by notches 68 in their peripheries in order that they may be oriented to correct position, or, if preferred, the knobs may be geared together for operating the same in unison and thereby adjust the grids and maintain them constantly in parallelism.

I claim:

l. An electron discharge device comprising a cylindrical cathode, cylindrical and coaxial grids within and coaxial to the cathode, means between said grids for providing a eld-free space therebetween, and said cathode .being spaced radially outward from said means so the electrons from the cathode pass therethrough as a radially converging beam, and a collector coaxial within said grids for receiving said electrons.

2. An electron discharge rdevice comprising eylindrical means for producing an electron stream in a path converging substantially perpendicular to the axis of said cylindrical means, a second cylinder constituting a resonator and of less diameter than and coaxial with the first said cylindrical means, said resonator having a radial passage for electrons therethrough radially inward from said first cylindrical means and having radially extending means therein shielding a part of said electron path through the resonator and adapted to provide a eld free passage for the electrons through said shielded part of the path, said resonator and said radial means adapted to cooperate for bunching electrons from said cylindrical means and extracting energy therefrom, a collector centrally disposed about said axis and in the path of convergence of said electrons, and means extending from and for cooling said collector.

3. An electron discharge device comprising cylindrical means for producing an electron stream in a path converging substantially perpendicular to the axis of said cylindrical means, a second cylinder constituting a resonator and of less diameter than and coaxial wtih the iirst said cylindrical means, said resonator having a radial passage for electrons therethrough radially inward from said rst cylindrical means and having radially extending means therein shielding a part of said electron path through the resonator and adapted to provide a eld free passage for the electrons through said shielded part of the path, said resonator and said radial means adapted to cooperate for bunching electrons from said cylindrical means and extracting energy therefrom, a collector centrally disposed about said axis and in the path of convergence of said electrons, said collector having a plurality of outwardly opening cavities for collection of electrons therein, and means extending from and for cooling said collector.

4. An electron discharge device comprising a cylindrical cathode, a heater next said cathode, said heater comprising a plurality of heater coil sections end to end and electrically spaced apart, said sections beingr connected in parallel for simultaneous use, and a central collector within said cathode, whereby electrons from the cathode converge radially therefrom to the collector.

5. An electron discharge device comprising a resonator cylinder of annular cross-section having two fixed coaxial cylindrical walls forming a resonator cylinder of annular cross section, said cylinder being divided medially by a third coaxial cylinder thereby forming outer and inner resonators of which one is larger than and encircles the other, parallel plates in said annular resonator cylinder supported by said third cylinder and vleaving gap openings of fixed dimension at the peripheries of said plates between said plates and the said two fixed coaxial cylindrical walls, and cathode means outside of the outer one of the said two fixed concentric cylindrical walls for producing converging streams of electrons through said two cylindrical walls and through the region between said plates, whereby electrons in most separated relation pass the gap of the larger resonator and the electrons in more concentrated relation pass the gap of the smaller resonator and whereby the larger one of said resonators aiects the electron velocity to bunch the electrons while in separated relation and the other resonator absorbs more energy from the more concentrated and bunched electrons.

6. An electron discharge device comprising a resonator cylinder of annular cross-section having two coaxial cylindrical walls of flexible and resilient material and of which one is within the other, said cylinder being divided medially by a third coaxial cylinder thereby forming outer and inner resonators each of which has one of said flexible walls as a wall thereof, parallel plates in said annular resonator cylinder supported by said third cylinder and leaving gap openings of variable dimension at the peripheries of said plates between said plates and the said two ilexible and resilient walls, cathode means girdling said cylinder for passing a modulated stream of electrons through the said cylinders and through the region between said plates for enabling energy to be derived from said stream by one of said resonators, and adjustable means .connected to said walls for flexing said flexible walls and thereby tuning the device. i

7. An electron discharge device comprising resonator cylinder of annular cross-section having two coaxial cylindrical walls of flexible and resilient material and of which one is within the other, said cylinder being divided medially by a third coaxial cylinder thereby forming outer and inner resonators each of which has one of said exible walls as a wall thereof, parallel plates in said annular resonator cylinder supported by said third cylinder and leaving gap openings of var.. iable dimension at the peripheries of said plates between said plates and the said two flexible and resilient walls, cathode means girdling said cylinder for passing a modulated stream of electrons through the said cylinders and through the region between said plates for enabling energy to be derived from said stream by one of said resonators, and adjustable means connected to said walls for flexing said exible walls and thereby turning the device, said means for flexing said flexible walls providing knobs on the exterior of the device and pressure-applying means on the flexible walls operatively connected to said knobs.

8. An electron discharge device comprising a resonator cylinder of annular cross-section having two coaxial cylindrical walls of flexible and resilient material and of which one is within the other, said cylinder being divided medially by a third coaxial cylinder thereby forming outer and inner resonators each of which has one of said flexible walls as a wall thereof, parallel plates in said annular resonator cylinder supported by said third cylinder and leaving gap openings of variable dimension at the peripheries of said plates between said plates and the said two flexible and resilient walls, cathode means girdling said cylinder for passing a modulated stream of electrons through the said cylinders and through the region between said plates for enabling energy to be derived from said stream by one of said resonators, and adjustable means connected to said walls for flexing said flexible walls and thereby tuning the device, said means for flexing said flexible walls providing bands on the flexible walls movable axially and adapted thereby to flex said walls, and said means for flexing said ilexible walls also providing exterior rings connected with vacuum seal to said bands.

9. An electron discharge device comprising a resonator cylinder of annular cross-section having two coaxial cylindrical walls of flexible and resilient material and of which one is within the other, said cylinder being divided medially by a third coaxial cylinder thereby forming outer and inner resonators each of which has one of said flexible walls'as a wall thereof, parallel plates in said annular resonator cylinder supported by said third cylinder and leaving gap openings of vai'- iable dimension at the peripheries of said plates between said plates and the said two flexible and resilient walls, cathode means girdling said cylinder for passing a modulated stream of electrons through the said cylinders and through the region between said plates for enabling energy to be derived from said stream by one of said resonators, and adjustable means connected to said walls for flexing said flexible walls and thereby tuning the device, and threaded knobs having grooves receiving said rings and adapted to move ksaid rings and bands axially by rotation of said knobs.

ALFRED H. LAIDIG. 

